The state would have gained only one additional seat had the census counted just U.S. citizens, one researcher found.

It's a strange and little known quirk of the census process — that people who cannot vote help influence future elections — which in 2010 helped Florida at the expense of states like Ohio, Pennsylvania and Missouri.

The methodology has politicians in states that lost seats angry and also puts some Florida Republicans in an awkward position, given tough talk recently over illegal immigration.

Last February, as Marco Rubio waged what proved to be a successful campaign for the U.S. Senate, he ran into criticism when he advocated that only legal U.S. citizens be counted for the purpose of awarding congressional seats. He quickly backtracked, saying he thought the census should also count legal residents, but not illegal immigrants.

Rubio was unavailable to speak for this story, spokesman Alex Burgos said.

How seats get divided

Imagine a reshuffling of the 435 U.S. House seats. The Constitution guarantees each state one seat, so scratch off the first 50.

The census count then helps allocate seats 51-435, one at a time. While there will be one House member for every 710,767 people, that's not necessarily how the Census Bureau decides how many congressional seats a state receives.

Here's how they do it. All 50 states and their populations are ranked in order. California, being the largest, is at the top, and gets the 51th congressional seat.

Next, the Census Bureau uses a formula to subtract from California's population the portion of the state assigned to that 51st seat.

So now Texas has the highest remaining population, and gets the 52nd congressional seat. Again, some of the state's population is subtracted. And so it goes, with the next seat awarded to the state with the largest remaining population, and that portion of the population removed until seat 435 is awarded.

In every case, the state with the highest remaining number gets the seat, though the margins are much smaller as the apportionment reaches the last 10 or so seats.

The state ranked 436 gets nothing.

Utah was unlucky 436 in 2000, losing out on a fourth congressional seat by 80 people. This year, North Carolina missed out by an estimated 16,000 people.

Noncitizens count

Using that process, Florida received the two additional House seats and will keep them until at least 2020.

But that's only because the entire population was counted.

Clark Bensen, who analyzes political and demographic data for a company he founded called Polidata, estimates that if the census counted only U.S. citizens for the purpose of apportionment, Florida would gain just one seat, not two.

Bensen used the same formula the Census Bureau does to hypothetically award congressional seats, but in his calculations he counted only U.S. citizens. Doing that would drop Florida's population from 18.8 million to 17 million, and cost Florida a congressional seat. There's a slight margin of error in Bensen's calculation, he admits, because the 2010 census does not include citizenship details, so he relied on 2009 census data.

But according to Bensen, if the census counted only U.S. citizens, California would have lost five congressional seats, while Montana, North Carolina, Oklahoma and Indiana each would have gained a seat.

"It's one of the things most people don't realize," Bensen said. "The census count, indirectly, sort of gives noncitizens a vote."

Calls for change

Along with congressional seats, the 10-year census count is used to allocate $400 billion in federal funding.

In 2009, Sen. David Vitter, R-La., proposed adding a question to the 2010 census asking about citizenship status to reshape how seats were awarded and how money might be divided. But the measure failed. And as a result, Vitter's Lousiana will lose a congressional seat.

"Louisiana stands to lose clout in Congress, while states that welcome illegal immigrants stand to unfairly benefit from artificially inflated population totals," Vitter said.

And some question the counts' constitutionality.

John S. Baker, who teaches constitutional law at Louisiana State University, said the Constitution specifically says "Indians not taxed" are not to be counted when considering congressional apportionment. To Baker, those sovereign Native American tribes are no different from foreign nationals living in the United States.

But others argue that the Constitution proves the opposite. Right before "Indians not taxed," the 14th Amendment to the Constitution said the census should be used to count "the whole number of persons in each State."

"The wording in the Constitution strongly suggests to me that the framers intended the census to count everybody," said Steve Schwinn, who teaches at the John Marshall Law School in Chicago.

Legal or not, Florida state legislators are expected to begin discussing how to add two new congressional districts during the 2011 legislative session.